update check fails with error messages

Starting a couple days ago, the update manager appears to be failing. The menubar has that warning triangle, telling me that updates havent happened for 35 days, and when I open Update Manager, it tells me there are no updates to install . If I click on the "check" button,I get the error window about failng to reach repositories, full error message follows below. I do have full internet access, i.e. web browsers, and apt-get run just fine. Any ideas? -- some corrupt files somewhere I need to delete?